Inorganic crystalline binders for electrophotographic plates

ABSTRACT

An electrophotographic material is disclosed comprising a support substrate and an inorganic crystalline photoconductive insulating layer. The photoconductive coating comprises a photoconductive material and an inorganic crystalline binder.

United States Patent inventors Alan B. Amidon;

Joseph M ammino; Richard Radler, all of I'enlield, N.Y. Appl. No. 829,835 Filed Apr. 4, I969 Division of Ser. No. 546,844, May 2, 1966. Patented Sept. 21, 1971 Assignee Xerox Corporation Stamford, Conn.

[5 l] Int. Cl ..G03gl3/22, 003g 5/04 [50] Field of Search 96/1 .5, 1.8; 252/50l [56] References Cited UNITED STATES PATENTS 3,396,016 8/1968 Olson 96/1 .8 3,406,063 10/1968 Mathin et al 96/1 .5

Primary Examiner-George F. Lesmcs Assistant Examiner-lohn C. Copper, lll Attorneys-Stanley Z. Cole and James J. Ralabatc ABSTRACT: An electrophotographic material is disclosed comprising a support substrate and an inorganic crystalline photoconductive insulating layer. The photoconductive coating comprises a photoconductivc material and an inorganic crystalline binder.

INORGANIC CRYSTALLINE BINDERS FOR ELECTROPHOTOGRAPHIC PLATES This application is a divisional of application Ser. No. 546,844, filed May 2, 1966.

Lithographic printing is a well known and established art. in general, the process involves printing from a flat plate, depending upon different properties of the image with the nonimage areas for printability. in conventional lithography, the nonimage area is hydrophilic while the image area is hydrophobic. in the lithographic printing process, a fountain solution is applied to the plate surface which wets all portions of the surface not covered by the hydrophobic image. This solution keeps the plate moist and prevents it from scumming up. An oil based printing ink is applied to the image surface depositing the lithographic ink only on the image area, the hydrophilic nonimage area repelling the ink. The ink image may then be transferred directly to a paper-sheet or other receptive surface, but generally it is transferred to a rubber offset :blanket which in turn transfers the print to the final paper sheet. Hence, for each print made during a run, a lithographic plate is first dampened with an aqueous fountain solution and then inked with a lithographic ink and finally printed.

it has been known that lithographic plates can be made in a photoconductive system by utilizing the conventional developed xerographic plate as a lithographic printing plate. In these systems, usually a zinc oxide type plate is charged by conventional means, exposed to the image to be reproduced and developed with conventional xerographic toner. The toner is generally hydrophobic in nature as is the background of the conventional binder type xerographic plate. In order that the developed xerographic plate be useful as a lithographic master, a differential must be established between the toner image and the background of the plate. Since both are hydrophobic in nature, it has heretofore been required that the background photoconductive component of the xerographic plate be treated either by the use of a conversion solution or by complete removal such as with a selective solvent, to make the background surface hydrophilic in nature. After the alteration of the nonimage, background area, the plate is then wetted with a nonaqueous or oil based ink whereby the toner will accept the ink and the new hydrophilic background will repel the ink.

While basically these systems have been found useful for lithographic purposes, there are inherent disadvantages to their use. One disadvantage, for example, is the fact that it is required in one instance that a conversion solution be used to convert the initially hydrophobic background to one which is hydrophilic so that it will not accept the oil based ink in the inking step. A second disadvantage is that in the approach wherein a solvent is used to remove the hydrophobic background, not only is an additional time consuming step required as with the use of the conversion solution, but such a treatment leads to a degradation of the quality of the image that is subsequently produced from the plate. A further disadvantage to the present existing technique is that generally they require the application of wet processes which inherently make the procedures undesirable.

It is, therefore, an object of this invention to provide a lithographic imaging system which will overcome the above noted disadvantages.

It is a further object of this invention to provide a novel method for the preparation of a lithographic master.

Another object of this invention is to provide an imaging system utilizing a novel lithographic master prepared from a xerographic plate.

Still a further object of this invention is to provide an imaging system wherein the novel lithographic plate can be prepared without utilizing image degrading treatments.

An additionalobject of this invention is to provide a process of using a novel lithographic printing master.

Yet, still a further object of this invention is to provide a completely dry'process for preparing of lithographic master.

The foregoingobjects and others are accomplished in accordance with this invention, generally speaking, by providing a lithographic master prepared by loosely fixing to the surface of a hydrophilic receiving substrate a photoconductive crystallinclike binder insulating layer. The photoconductive layer of the present invention is prepared by dispersing a particulate photoconductive material such as zinc oxide in a crystallin'elike binder material such as tetrachlorophthalic anhydridc (TCPA). It has been found that blending the two in equal proportions will produce optimum results. The photoconductive layer can then be electrostatically charged and imaged in accordance with the conventional xerographic'imaging process more fully described in US. Pat. No. 2,297,691. The electrostatic latent image is developed with a hydrophobic developer and the resulting developed image fixed. As a resultof the physical structure of the binder material, it has been observed that the developer material penetratesthe intertices of the binder particles andis affixed to the surface of the substrate thereby forming a network of binder particles dispersed or trapped within the bounds of the impinging developer material. The plate is then subjected to a gentle nonstatic surface treatment which removes from the background areas the photoconductive insulating material not protected by the fixed toner image. There is thus produced a lithographic master having hydrophobic image areas and 'hydrophilic background areas. The lithographic master can then be used to continuously make prints whereby a lithographic ink is applied to the master, the ink adhering selectively to the surface of the hydrophobic or oleophilic toner image, andthe master subsequently contacted with a copy sheet to transfer the image. Alternatively, the ink image may initially be transferred to the surface of an offset blanket from which it is in turn transferred to the final copy sheeL'lt is to be understood that if it is desired to develop the electrostatic latent image of the present invention with a hydrophilic developer, the background, nonimaged-area of the hydrophilic plate may be treated in such a manner such as by spraying with an isoparafinic aliphatic hydrocarbon, so as to exhibit oleophilic properties or by initially using a substrate having hydrophobic properties thereby producing a reverse lithographic plate.

Furthermore, the process of the present invention; may be used, if desired, to prepare a xeroprinting master. In .this instance, the material which is to serve as the baseof the printing plate is such that when the imaged plate is exposed toan electrical charge, the image areas of the plate will retain the charge while the nonimage areas, i.e., those areas from which the loosely bound photoconductive insulating material has been removed, no longer being insulated, will not retain a charge. A printing master prepared in this manner need only be charged and developed to reproduce copies of the original image, thereby eliminating the necessity of reimaging the printing plate. On uniformly charging the plate, the electrostatic charge would be retained only on the light insensitive image areas, the electrically conductive background area serving as a sink, thereby permitting the charge to leak off.

it has been found that when a particulate photoconductive material is dispersed in the crystallinelike binder material of the present invention and the resulting photoconductive compositionfixed to the surface of a suitable hydrophilic substrate, the bond which exists between the resulting photoconductive binder material and the substrate is such that the photoconductive layer may easily be removed by a gentle nonstatic surface treatment which will neither affect the developed image nor the quality of the print produced therefrom. It is hypothesized that the bonding effect realized between the binder material of the present invention and the underlying substrate is due to the structural nature ofthe binder composition. It is generally consideredthat the materials suitable for use exhibit properties typical of crystalline substances but although they exhibit these properties, need not have a definite crystalline structure and may be amorphousin nature. Therefore, the phrase crystallinelike" is used in the course of the present invention to define a binder material whichwill yield the necessary bonding effect described above nonimaged or background area of the crystallinelike photoconductive insulating material exposes the hydrophilic surface of the underlying substrate. The plate thus produced comprises a hydrophilic substrate with an oleophilic toner image fused thereon. As a result of having started with a substrate processing hydrophilic properties, it is no longer necessary to treat the surface of the imaged plate in order to establish the differential needed for lithographic printing as is generally required by the conventional lithographic plates as taught in U.S. Pat. Nos. 3,107,169; 3,00l ,872; and 3,158,476.

in accordance with the present invention, a photoconductive material is blended with a crystalline or crystallinelike binder composition in proportions of about 25 to 1.5 parts photoconductor to about 7 to 0.5 parts crystalline binder. lt has been found that about I part photoconductive material to about 1 part of the binder composition will give optimum results. The finely divided photoconductive particles and the crystalline binder material are desirably mixed in a liquid such as acetone by any suitable means such as in a paint shaker. The solvent is added in the proportions sufficicnt to thin the mixture to a desirable coating consistency. Alternatively, the binder composition may be initially dissolved in a solvent therefor, and subsequently dispersed with the photoconductor particles. The resulting photoconductive composition is then applied to the desired surface by flow coating, dipping, spraying, electrostatically, with a doctor blade, or by any other suitable coating operation. The coating is dried at the necessary temperature to loosely affix the particular photoconductive composition to the substrate thereby producing a uniform layer of the photoconductive pigment dispersed in the crystallinelike binder composition. The drying temperature and time will vary depending upon the particular binder composition in use. For example, if the crystalline binder material is eugenol (4-allyl-2-methoxy phenol) an applicable temperature range will be from about 30 to 80 C. for approximately 10 to minutes.

The resulting photoconductive plate is electrostatically charged in the dark and the charged surface selectively exposed to a light source to produce a latent image. The imaged surface is then developed with hydrophobic electroscopic marking particles or toner, the developer adhering to the areas corresponding to the latent image. The developed image is then heat fused. Any suitable means may be used to fix the developed image to the surface of the hydrophilic substrate. ln addition to the heating approach, the fusing procedure may be carried out by exposure to solvent vapors, a process more fully described in U.S. Pat. No. 3,l40,l60. It is also possible when the image is fused by the application of heat to develop the electrostatically charged image with a liquid developer containing charged hydrophobic particles suspended in a carrier liquid which is vaporized during the fixing of the image. A light pressure is then applied to the surface of the photoconductive plate by any suitable means such as by brushing or by directing a draft of air from a blower onto the surface of the plate, thereby disengaging the loosely bound photoconductive composition-and exposing the hydrophilic underlayer. The duplicating plate is then fastened to a press cylinder of a lithographic press. The printing operation is carried out utilizing commercially available fountain solutions and lithographic inks. The electroscopic particles used to develop the electrostatic latent image comprise a resin which is hydrophobic in nature and which may be readily wetted by a lithographic ink.

When in the fixed condition, the image on the printing surface of the crystalline binder photoconductive plate of the present invention is tenaciously held to the surface of the substrate and shall neither be pulled away by printing ink nor washed away by the wet-out or fountain solutions. Furthermore, the nonimage hydrophilic background areas of the plate are readily wetted by the fountain solutions and hold a film thereof on the surface of the nonimage areas and do not permit the aqueous film to be displaced therefrom by the lithographic printing ink.

Any suitable insulating composition which has a softening point temperature somewhat greater than the toner material used to develop the electrostatic latent image, and is crystalline in nature or capable of being formed into particulate crystallinelike matter so as to produce the necessary adhesive properties as discussed above may be used in the course of the present invention.'For example, when a developer composition comprising polystyrene is used to develop the electrostatic latent image, the particulate or crystalline binder composition should generally have a melting temperature substantially greater than that of the toner, i.e., the polystyrene composition, so as not to destroy the porous nature and loosely adhering properties of the binder composition. Typical nonpolymeric organic crystalline binder compositions are: 4-allyl- 2-methoxyphenol, tetrachlorophthalic anhydride, phthalic anhydride, acetophenetidin, acetyl phenyl hydrazine, aconitic acid, adipic acid, agaric acid, para-amino azo benzene, azo benzene, benzoic acid, n-tcrt-butyl acrylamide, cetyl alcohol, 3,4-dichlorobenzaldehyde, di-cyclopentadiene dioxide, dimethyl-terephthalate, di-phenyl-guanidine, furoic acid, hexachloroethane, hydroquinone, isophthalic acid, lauric acid, maleic acid, maleic anhydride, melamine, myristic acid, betanaphthyl-methyl ether, palmitic acid, phenazine, phenolphthalein, ortho-phenyl-phenol, para-phenyl-phenol, phenyl salicylate, pimelic acid, salicylic acid, sebacic acid, sulfo-salicylic acid, and mixtures thereof. Typical inorganic crystalline binders are the phosphonitrilic compounds as more fully described in Chemical Reviews, 62,247 (1962). Exemplary of these compounds are the cyclophosphazenes including cyclotetraphosphazene and cyclotriphosphazenc, and halogencyclophosphazene, including hexachlorocyclotriphosphazenc, among others. Preferred among the crystalline binder materials are the organic nonpolymcric composition which due to the nature of their crystalline structure more readily satisfy the requirements of the present invention as to the degree of bonding desired between the binder and the underlying substrate. Other typical binder insulating materials are silicone resins such as DCl, DC+804, and DC-996 commercially available from the Dow Corning Corporation; acrylic and methacrylic ester polymers such as Acryloid A10 and Acryloid B72, polymerized ester derivatives of acrylic and alpha-acrylic acids both commercially available from Rohm & Haas Company, and Lucite 44, Lucite 45 and Lucite 46, polymerized butylmethacrylates commercially available from E. l. duPont de Nemours & Company; chlorinated rubber such as Parlon, commercially available from the Hercules Powder Company; vinyl polymers and copolymers such as polyvinyl chloride and polyvinyl acetate, including Vinylitc VYNH and VMCH, commercially available from the Bakelite Corporation; cellulose esters and ethers such as ethyl cellulose and nitrocellulose, and alkyd resins such as Glyptal 2469, commercially available from the General Electric Company.

Any suitable photoconductive material may be used in the course of this invention. Typical inorganic photoconductive materials are sulfur, selenium, zinc sulfide, zinc oxide, zinc cadmium sulfide, zine magnesium oxide,.cadmium selenide, calcium strontium sulfide, cadmium sulfide, mercuric iodide, mercuric oxide, mercuric sulfide, indium trisulfide, gallium triselenide, arsenic disulfide, arsenic trisulfide, arsenic triselenide, antimony trisulfide, cadmium sulfoselenidc, doped chalcogenides of zinc and cadmium, bismuth oxide, molybdenum oxide, lead oxide, molybdenum oxide, molybdenum selenide, molybdenum sulfide, molybdenum telluride, aluminum selenide, aluminum sulfide, aluminum telluride, bismuth iodide, bismuth selenide, bismuth sulfide, bismuth telluride, cadmium telluride, mercuric selenide, mercuric telluride, lead oxide, lead selenide, lead sulfide, lead telluride, cadmium arsenide, lead chromate, gallium sulfide, gallium telluride, indium sulfide, indium selenide, indium telluride, red lead and mixtures thereof. Typical organic photoconductors include triphenyl amine phthalocyanine, Monastrol Red B, a quinacridone commercially available from E. l. du Pont de Nemours 8L Company, calcium lake of l-(2'-azonaphthalene-1'-sulfonic acid)- 2-naphthol; 8, l 3-dioxodinaphtho-( l ,2-2,3 )-furan-6-carbox- 4"-methoxyanilide; 3,3'methoxy-4,4-diphenyl-bis( 1"-azo- 2"-hydroxy3"-napthanilide); 2,4,bis-(4,4-diethyl-aminophenyl)-l,3,4-oxadiazol; 4,5-diphenyl-imidazolidinone; 4,5- diphenyl-imidazolidinethione; 4,5-bis-(4-amino-phenyl)- imidazolidinone; 1,5-cyanonaphthalene; 1,4-dicyanonophth alene; amino-phthalodinitrile; nitrophthalidinitirile; 1,2 ,5 ,6-tetraazacyclooctatetraene-( 2,4,6,8 3,4-di-( 4 methoxy-phenyl)-7,8-diphenyl-1,2,5,6-tetraaza-cyclooctatetraene-(2,4,6,8); 3,4-di-(4-phenoxy-phenyl)-2,4,6,8); 7,8-diphenyll ,2,5 ,6-tetraaza-cyclooctatetraene-(2,4,6,8);

3,4-di-(4'-phcnoxy-phenyl)-7,8-diphcnyl-1,2,5,6-tetraazaeyclooctatetraene-(2,4,6,8); 3,4,7,8-tetramethoxy-l,2,5,6- tetraza-cyclooctate-traenc-(2,4,6,8); Z-mercaptobenzthiazole; Z-phenyl-4-alpha-naphthylideneoxazolone; 2- phenyl-4-diphenylide-oxazolone; 2-phenyl-4-p-methoxybcnzylideneoxazolone; 6-hydroxy-2-phenyl-3 -(pdimethylamino phenyl)-benzofuran; 6-hydroxy-2,3-di (pmethoxy-phenyl) benzofurane; 2,3,5,6-tetra-(p-methoxyphenyl)-furo-(3,2')-bcnzofurane; 4-dimethylaminobenzylidene benzhydrazide; 4-dimethyl-aminobenzylideneisonicotinic acid hydrazide furfurylidene-(2)-4- dimethylaminobenzhydrazide; S-benzilidene-aminoacenaphthene; 3-benzylidene-amino-carbazole; (4-N,N- dimethyl amino-bcnzylidene)-p-N,N-deimethylaminoaniline; (2-nitro-benzylidene)-p-bromo-aniline; N,N-dimethyl-N-(2- nitro4-cyano-benzylidene)-p-phenylene-diamine; 2,3- diphenyl-quinazoline; 2-(4'-amino-phenyl)-phenyl-quinazoline; 2-phenyl-4-(4'-di-methyl-amino-phenyl)-7-methoxyquinazoline; 1 ,3-dephenyl-tetrahydroimidazole; 1,3-di-(4'- chlorophenyl )-tetrahydroimidazole; l,3-diphenyl-2-4- demethyl-amino Phenyl)-tetrahydroimidazole; 1,3-di-(ptolyl)-2-quinoly-(2' )-tetrahydro-imidazole; 3-(4- dimcthylamino-phenyl)-5-(4"-methoxy-phenyl)-6-phenyl- 1,2,4-triazine; 3-pyridyl-(4')-5-(4"-dimethyl-amino-phenyl)- 6-phenyl-1,2,4-triazine; 3-(4'-amino-phenyl)-5,6-di-phenyll,2,4-triazinc; 2,5-bisl 4-aminophenyl-( l H I ,3,4-triazole; 2,5-bisl4'-N-cthyl-N-aeetylamino)-phenyl-(1)-]1,3,4- triazole; S-diphenyl-B-methyl-pyrazolinc; l,3,4,5-tetraphcnylpyrazoline; l-phenyl-3-(p-mcthoxy styryl)-5-(p-methoxy-pehnyl)-pyrazoline; l-methyl-2-(3-4'-dihydroxy-methylencphenyl)-benzimidazole; 2-(4'-deimethyl-amino phenyl)- benzoxazole; 2-(4'-methoxyphenyl)-benzthiazole;-2,5-bis-[ aminophenyl( l 1,3,4-oxadiazole; 4,5-diphenyl-imidazole; 3-aminocarbazole; mixtures thereof. In addition, other typical photoconductors are charge-transfer type photoconductors such as disclosed in copending application Ser. Nos. 426,409; now U.S. Pat. No. 3,408,183 Ser. No. 426,423; now U.S. Pat. No. 3,408,184; and Scr. No. 426,431 now U.S. Pat. No. 3,408,186 Ser. No. 426,428; now U.S. Pat. No. 3,408,185; Ser. No. 426,396 now U.S. Pat. No. 3,408,182. It was found in the case of the organic photoeonductor pigments that best results were obtained when the photoconductive pigment was encapsulated with a resinous composition. Therefore, when it was desired to use the organic photoconductor pigments, the latter were spray dried in the presence of an organic synthetic resinous material such as polyvinyl earbazole, prior to dispersion in the crystallinelike binder composition. It was felt that this latter treatment enhanced the charge retention properties of the photoconductive binder layer, thereby increasing its usefulness for the present invention. Any suitable encapsulating resinous material may be used when the photoconductive material of the present invention is organic in nature. Typical such resinous materials are polyethylene terephthalate, polystyrene, polyvinylcarbazole, and thermosetting resins such as urea formaldehyde and epoxy resins. Any conventional and/or suitable encapsulating technique known to the prior art such as disclosed in U.S. Pat. No. 2,800,457 may be utilized. Preferably, in the selection of the photoconductive pigment of the present invention, it was desired to utilize the inorganic pigments inasmuch as optimum properties could be obtained while involving the necessity of an encapsulating step generally preferred when using the organic photoconductive pigments.

The thickness of the photoconductive insulating layer of the present invention may vary from about 2 microns to about microns. It is preferred that the layers be from about 6 to about 25 microns thick in order to achieve optimum results, thereby providing maximum electrostatic contrast. The desired thickness may be built up by multiple coatings, if necessary.

Any suitable material may be used as the substrate for the lithographic master of this invention. The base or substrate used in preparing lithographic binder plates according to the present invention provides physical support for the photoconductive insulating layer and also should have an electrical resistance somewhat less than the photoconductive layer so that it will act as a ground when the electrostatically charged coating is exposed to light. The base should always be hydrophilic in nature or be so treated so as to possess hydrophilic properties in order to provide the necessary surface differential. Typical materials are aluminum, brass, conductive glass, steel, e.g., stainless and low carbon, copper, nickel, zinc alloys and mixtures thereof. If reverse lithography is practiced, as discussed above, then a hydrophobic substrate would be used. Other materials having electrical resistances and surface properties similar to the aforementioned can also be used as the base material to receive the photoconductive layer thereon. Other nonconductive materials such as thermoplastics may be used as the backing for the lithographic plate. When used, however, it is necessary to charge both sides of the plate dur' ing the imaging phase of the preparation of the plate according to the process set out in U.S. Pat. No. 2,922,883. When a conventional lithographic plate is the desired product then it is preferred to employ a hydrophilic substrate.

Any suitable wet-out or fountain solution may be used in the course of this invention. Typical such fountain solutions are 1 percent solutions by volume of gum cellulose and water, gum arabic and water, glycerol and water and isopropyl alcohol and water. Distilled water may also be used as the wet-out solution. Other suitable fountain solutions are disclosed in U.S. Pat. No. 3,107,169. The fountain solutions may contain other constituents, such as, for example, formaldehyde and if glycerin is not present, it may be added primarily to take advantage of its hygroscopic nature and hence by absorption of water, prolong the period during which the hydrophilic surface of the lithographic plate retains its hydrophilic properties. The formaldehyde additives will also achieve this effect. Therefore, the fountain solutions containing the glycerin, formaldehyde additives or mixtures thereof are preferred inasmuch as the resulting lithographic plates can be kept before use for relatively long periods of time as compared to those plates treated with a fountain solution not containing the respective additive. Solutions containing gum arabic are also found to be very effective inasmuch as a lithographic plate treated with such a solution is found to retain its hydrophilic properties in the nonimaged areas for relatively long periods of time following removal from the press. As a result, the resulting printing plate can be reused without subjecting it to an additional treatment with a fountain solution.

Any suitable toner or developer may be used in the course of this invention such as those in U.S. Pat. Nos. 2,788,288; 3,079,342; and Re 25,136. The toner is generally a resinous material which when fixed has hydrophobic properties and will accept oily inks. Typical such developer powders are styrene polymers, polymers of substituted styrenes for example, Piccolastics, commercially available from the Pennsylvania Industrial Chemical Corporation, phenol formaldehyde resins, as well as other resins having hydrophobic properties. The developer powder may be applied directly to the latent image or admixed with a carrier such as glass beads. The toner may be applied in the form of a mixture with magnetic parti cles such as magnetic iron to impart a charge to the developer powder particles triboelectrically. The developer or toner particle is so chosen that it is attracted electrostatically to the charged image or repelled from the background area to the charged image and held thereon by electrostatic attraction. If a negative charge is applied to the photoconductive insulating material, a positive toner is used which adheres to the negatively charged image. If the charge applied is such that the latent image retains a positive charge, then a negative toner will be applied.

As mentioned above, liquid developers may also be used in the course of this invention. Such developers are disclosed in U.S. Pat. Nos. 2,890,174; and 2,899,335. Generally, the developer comprises a liquid combination of mutually compatible ingredients, which when brought into contact with an electrostatic latent image, will deposit upon the surface of the image in an image-wise configuration. In its simplest form, the composition comprises a finely divided opaque powder, a high resistance liquid and an ingredient to prevent agglomeration. Liquids which have been found suitable include such organic high resistance liquids as carbon tetrachloride, kerosene, benzene, tetrachloroethylene and any substituted hydrocarbon having a boiling point between about 70 and 200 C. Any of the finely divided opaque solid materials known in the art such as carbon black, talcum powder, or other pigments may be used in the liquid developer. Silica aerogel, commercially available from Monsanto Chemical Company, is a deagglomeration ingredient generally used. However, any conventional and/or suitable ingredient known to be useful by the prior art in a liquid development system may be utilized.

Any suitable development means may be used in the course of this invention, such as cascade development more fully described in U.S. Pat. Nos. 2,618,55l and 2,618,552, powder cloud development more fully described in U.S. Pat. Nos. 2,725,304 and 2,918,9l0, and magnetic brush development, as more fully described in U.S. Pat. Nos. 2,791,949 and 3,015,305. As a result of the nature of the bond which exists between the photoconductive crystallinelikc binder layer and the underlying substrate, as is more fully described above, the powder cloud development technique is preferred, so as to minimize the possibility of disturbing the loosely held photoconductive binder layer.

Any suitable lithographic ink may be used in the course of this invention. Typical such lithographic inks and their properties are disclosed in Printing Ink Technology" by E. A. Apps, Chapter 1, Chemical Publishing Co., lnc., New York, New York, I959. The inks are of the same fundamental style as good quality letterpress inks, and the simplest type consist of a pigment mixture dispersed in a lithographic varnish- The lithographic or oil-based ink being oleophilic in nature adheres to the hydrophobic toner image, and is repelled by the hydrophil- 1C nonimage areas.

The invention is illustrated in the accompanying drawings in which:

FIG. 1 represents a magnified cross section through a photoconductive crystalline binder plate of the present invention prior to surface treatment;

FIG. 2 represents a magnified cross section through a lithographic printing plate of the present invention following removal of the loosely held photoconductive insulating material.

In the present process for preparing a lithographic plate 1 as illustrated in FIG. 1, a suitable substrate 2 is coated with a photoconductive insulating composition 3 comprising a photoconductive pigment 4 dispersed in a crystallinelike binder composition 5. On the surface of the photoconductive layer is superimposed a toner image 6 which is affixed to the surface of the substrate between the interstitial spaces of the photoconductive composition. The selection of the supporting substrate 2 is based upon the desired use of the lithographic plate such as to give the plate additional strength or to provide added flexibility in situations requiring it. FIG. 2 illustrates the lithographic plate 1 following removal of the photoconductive insulating material from the surface of the plate unprotected by the toner image 6, thereby exposing the hydrophilic surface 7 of the substrate 2.

To further define the specifics of the present invention, the following examples are intended to illustrate and not limit the particulars of the present system. Parts and percentages are by weight unless otherwise indicated. The examples are intended to illustrate various preferred embodiments of the present invention.

EXAMPLE 1 Equal parts of an organic binder composition, 4-allyl-2- methoxyphenol (eugenol) commercially available from Eastman Kodak Company, and a zinc oxide photoconductive material commercially available from New Jersey Zinc Co., are thoroughly mixed in a paint shaker for approximately 30 minutes. Acetone, containing about 0.02 parts of zinc acetate is added to the photoconductive-binder blend, and the mixing procedure repeated until the desired coating consistency of the composition is obtained, The resulting slurry is coated on a 7 mil grained Harris Alum-o-Lith Redi-Cote aluminum master base with a No. 14 wire wound bar to a thickness of about l0 microns. The resulting coated aluminum base is dried for approximately 13 minutes at a temperature of about 50 C. Following drying of the plate, the photoconductive coating is charged in the dark to a potential of about 200 volts with a three-wire corotron at a potential of about 7,500 volts, and the charged plate exposed to a test pattern with about 25 footcandle-seconds of white light. The resulting electrostatic latent image produced is then developed by magnetic brush development with a positively charged hydrophobic toner comprising a styrene terpolymcr. The toner image is then fused to the surface of the plate by the application of heat at a temperature of about 250 F. for about 5 seconds. Following cooling of the plate, the surface is rubbed with a dry cotton swab which removes the photoconductive binder material from the areas not protected by the fused toner image. The plate is then wrapped on the cylinder of a lithographic printing press and operated in the conventional manner using an Elfo desensitizer, an acidic gum solution available from Azoplate Corporation, as the fountain solution. A lithographic ink is then applied to the printing surface of the plate and the ink image transferred in imagewise configuration upon contact to the surface of a paper copy sheet. High quality prints are obtained.

EXAMPLE ll The process of example I is repeated excepting following the inking step the plate is first contacted with a rubber offset blanket and then transferred upon contact to the surface of a paper copy sheet. With the use of a rubber offset blanket, longer runs producing prints of higher quality are obtained.

EXAMPLE Ill The process of example I is repeated excepting the organic binder material used is tctrachlorophthalic anhydride in place of the eugenol. Prints comparable to those of example I are obtained.

EXAMPLE IV The process of example III is repeated excepting following the inking step the plate is first contacted with a rubber offset blanket and then transferred upon contact to the surface of a paper copy sheet. Copies of enhanced quality over those made without the offset blanket are obtained.

EXAMPLE V Monolite Fast Blue GS a metal-free phthalocyanine (aform) available from Arnold Hoffman Company is spray dried in the presence of polyvinyl carbazole and the resulting encapsulated photoconductive pigment dispersed in equal parts of tetrachlorophthalic anhydride crystalline binder com position. The remainder of the process is similar to that as described in example I with comparable results obtained.

EXAMPLE VI Monolite Fast Blue GS is spray dried in the presence of polyvinyl carbazole and the resulting encapsulated photoconductive pigment dispersed in equal parts of Eugenol. The remainder of the process is similar to that as described in example l excepting following the inking step the imaged plate is first contacted with a rubber offset blanket and then the ink image transferred upon contact to the surface of a paper copy sheet. The use of the rubber offset blanket increases the quality of the resulting prints.

EXAMPLE VII The process of example V is repeated excepting Monastral Red B (fi-form), a quinacridone commercially available from E. l. duPont de Nemours & Co., is substituted for the phthalocyanine pigment and conductively treated paper is substituted for the aluminum master base. In addition, the image is trans ferred intermediately to an offset blanket and from there transferred to the final copy sheet. The images obtained are similar to those produced by the plates utilizing the offset blanket as an intermediate step in the printing process as in examples ll and IV.

EXAMPLE Vlll About 6 parts of trimeric phosphonitrilic chloride are heated to about 50 C. and the temperature maintained until all of the trimer is melted. About l part of X-form metal-free phthalocyanine, prepared as described in copending U.S. Pat. application, Ser. No. 505,723, filed Oct. 29, 1965 now U.S. Pat. No. 3,357,989, is added to the melted phosphonitrilic chloride trimer and the mixture stirred. The resulting dispersion is coated on a 7 mil grain aluminum master base as in example with a No. 14 wire wound bar at a thickness of about 8 microns. The coated plate is cooled to a temperature of about 23 C. yielding a bluish crystalline coating. The photoconductive coating is charged in the dark to a potential of about 200 volts with a laboratory corotron unit powered by high voltage power supply. The charging current is about 0.1 of a milliamp at about 7,500 volts. The charged plate is exposed to a test pattern with about 25 foot-candle-seconds of white light. The resulting electrostatic latent image produced is then developed by powder cloud development with a positively charged hydrophobic developer toner comprising a styrene terpolymer. The toner image is then fused to the surface of the plate by the application of heat at a temperature of about 250 F. for about seconds. Following cooling of the plate, the surface is rubbed with a dry cotton swab which removes the photoconductive binder material from the area not protected by the fused toner image. The plate is wrapped on the cylinder of a lithographic printing press and operated in a conventional manner using a fountain solution consisting of a Elfo desensitizer. A lithographic ink is then applied to the surface of the plate and the ink image transferred upon contact to the surface of a paper copy sheet. The plate produces high quality images.

EXAMPLE [X The process of example Vlll is repeated excepting the ink developed image is first transferred to a rubber offset blanket and then transferred upon contact to the surface of a paper copy sheet. Higher quality images are obtained when the offset blanket is used.

EXAMPLE X The process of example VIII is repeated excepting cadmium sulfoselenide commercially available from Ferro Corp., Cleveland, Ohio, is substituted for the organic photoconductor pigment. The ink developed image is first transferred to a rubber offset blanket and then transferred upon contact to the surface of a paper copy sheet. lmages of a quality similar to those obtained in IX are realized.

EXAMPLE Xl A printing plate is prepared according to the process of example I up to and including the step of fusing the toner image to the surface of the plate. At this stage of the process, the plate is cooled, the photoconductive binder material brushed from the surface of nonimaged areas, and the resulting plate recharged in the presence of light to a potential of about -200 volts with a 3 wire corotron at a potential of about 7,500 volts so as to reestablish the latent image in those areas of the plate on which the electrically insulating image has been developed. The image is then contacted with electroscopic marking particles comprising a styrene terpolymer, with the particles adhering to the recharged surface of the originally developed image. The charged marking particles are then electrostatically transferred from the printing plate to the surface of a Harris Alumo-Lith aluminum substrate according to the process described in U.S. Pat. No. 3,004,860. The transferred image is then fused to the surface of the aluminum substrate by the application of heat at a temperature of about 250 F. for about 5 seconds. The resulting plate is then wrapped on the cylinder of a lithographic printing press and operated in the conventional manner as described in example I. The ink image produced is first transferred to the surface of a rubber offset printing blanket from where it is transferred upon contact to the surface of the final paper copy sheet. Acceptable prints were obtained.

Although the present examples are specific in terms of conditions and materials used, any of the above listed typical materials may be substituted when suitable in the above examples with similar results. In addition to the steps used to prepare the lithographic plate of the present invention, other steps or modifications may be used, if desirable. For example, the fountain solution and lithographic ink may be applied in a single step to the surface of the plate. In addition, other materials may be incorporated in the developer, ink, fountain solution, photoconductive material or xerographic plate which will enhance, synergize, or otherwise desirably effect the properties of these materials for the present use. For example, spectral sensitivity of the plates prepared in accordance with the present invention may be modified by incorporating photosensitizing dyes therein.

Anyone skilled in the art will have other modifications occur to him based on the teaching of the present invention. These modifications are intended to be encompassed within the scope of this invention.

What is claimed is:

1. An electrophotographic plate comprising a base substrate having fixed to the surface thereof an insulating layer of a photoconductive material dispersed in an inorganic crystalline binder, said binder consisting essentially of a phosphonitrilic compound.

2. The electrophotographic plate as described in claim 1 wherein the said inorganic crystalline binder material consists essentially of trimeric phosphonitrilic chloride.

3. The electrophotographic plate as described in claim 1 wherein said photoconductive material consists essentially of a phthalocyanine pigment.

4. The electrophotographic plate of claim 1 wherein said photoconductive material consists essentially of zinc oxide.

5. The electrographic plates as described in claim 1 wherein said photoconductive material consists essentially of cadmium sulfoselenide.

6. An electrophotographic imagining process comprising forming an electrostatic latent image on the surface of a photoconductive plate, said plate comprising a support substrate having fixed to the surface thereof a photoconductive material dispersed in an inorganic crystalline binder consisting essentially of a phosphonitrilic compound, developing said image with electroscopie marking particles and fixing said image to the surface of said photoconductive plate.

7. The process as disclosed in claim 6 wherein said inorganic crystalline binder material consists essentially of trimeric phosphonitrilic chloride. 

2. The electrophotographic plate as described in claim 1 wherein the said inorganic crystalline binder material consists essentially of trimeric phosphonitrilic chloride.
 3. The electrophotographic plate as described in claim 1 wherein said photoconductive material consists essentially of a phthalocyanine pigment.
 4. The electrophotographic plate of claim 1 wherein said photoconductive material consists essentially of zinc oxide.
 5. The electrographic plates as described in claim 1 wherein said photoconductive material consists essentially of cadmium sulfoselenide.
 6. An electrophotographic imagining process comprising forming an electrostatic latent image on the surface of a photoconductive plate, said plate comprising a support substrate having fixed to the surface thereof a photoconductive material dispersed in an inorganic crystalline binder consisting essentially of a phosphonitrilic compound, developing said image with electroscopic marking particles and fixing said image to the surface of said photoconductive plate.
 7. The process as disclosed in claim 6 wherein said inorganic crystalline binder material consists essentially of trimeric phosphonitrilic chloride. 